1. Field of the Invention
The present invention relates to image processing and, particularly, to an improved system and method for correcting defects in images.
2. Description of the Related Art
Digitized images often include imperfections that are not present in the original image. One cause of such defects may be the components of the image capturing system. For example, a scanning surface, or platen, may contain scratches and other optical path obstructions. These optical path obstructions are digitized along with the original image and appear as imperfections in the digitized image.
Another cause of imperfections is defects within the physical medium of the image. For example, a photograph, film negative or other physical medium may be scratched or deformed despite careful handling. In addition, dust, hair, smudges, and the like may be deposited on the surface of the physical medium and will be digitized along with the original image. These defects will also appear in the digitized image as defects.
Conventional software programs are available to identify such defects. Some programs simply identify anything in the image with a certain characteristic, such as high frequency content, as being defective. Other programs allow the user to manually specify the defects. The identification of such defects can be summarized in a defect map. A binary defect map simply marks pixels in an image as defective or non-defective. Other systems facilitate the creation of a continuous defect map, wherein each pixel is marked with a defect value proportional to the severity of any defect at the pixel.
Once a pixel has been marked as defective, conventional imaging programs replace the defective pixel with a replacement amplitude value determined from amplitudes of the surrounding pixels within a predetermined area. In particular, such programs define a fixed area around a defective pixel and then calculate a mean average of the amplitude values of the pixels within that area. This value is then used to fill the defective pixel.
Conventional defect correction programs have several technical disadvantages. For example, conventional defect correction programs generally employ a fixed correction area, wherein a significant number of defective pixels are included, which are then included in the correction averaging calculation. This, in turn, can cause defects in the corrected image.
These and other drawbacks in the prior art are overcome in large part by a system and method for correcting defects in an image according to the present invention. In accordance with one implementation of the present invention, a method for correcting images is provided. In accordance with this implementation, the correction area surrounding the defective pixel is dynamically chosen to include a predetermined percentage of non-defective pixels. The percentage is varied as a function of the size of the surrounding region, such that the percentage decreases as the size of the region increases.
According to another implementation of the present invention, the shape of the surrounding area may be varied to further enhance the correction procedure. According to this method, subregions surrounding the defective pixel are defined. Once the subregions surrounding the pixel has been defined, the pixel is corrected, for example, by choosing a median average of the pixel amplitudes within the subregions.
Thus, the defect correcting system and method provides an improved method for selecting a replacement value for a defective pixel. This results in a clearer final image having fewer defects than in many conventional imaging systems.